Endoscope Leak Testing

How many holes have been discovered by effective leak testing within the past year?

How many scopes have fluid invasion within the past year?

Is there a specific staff that performs leak tests?

When does leak testing occur?

Is trapped air removed prior to the evaluation? Is the scope pressurized prior to placing it in water?

Is the scope removed from the water before the scope is depressurized?

Leak testing is probably the most significant proactive diagnostic process you can perform on your endoscopes. Success or failure in performing it will have a major impact on your endoscope inventory. Implications can be negative or positive toward both your repair budget and patient safety. Cross contamination of chemicals and bio-burden pose a significant safety threat to your patients. Fluid damage to your scope inventory can essentially be eliminated when trained staff understand and commit to performing all steps in the appropriate sequence of pressure testing. Failure to leak test after every procedure greatly increases repair costs and decreases department efficiency.

Modern endoscopes are airtight, allowing the interstitial cavities to be pressurized in order to observe for leakage. While the hollowness of the main structural components of the endoscope allows pressure testing to be effective, it also means that fluid entering one area of the scope can travel the entire internal scope in a short period of time.

Standards for practice when mechanically pressurizing the scope to perform the leak test include:

Ascertain that the light guide prong is tight.

Connect the leak tester to the scope and ensure that the bending rubber is inflated prior to submersing the scope in water.

Make sure the scope is completely covered with water. Scope parts not immersed in water may have a hole that goes undetected.

Use water for the pressure test. Discoloration of enzymatic cleaners can minimize the viewer’s capability to see the entire scope. Leaks may also go undetected because they are considered bubbles created by the cleaning solution.

Remove all buttons and valves from the scope and coil it to the size of the sink. This will remove structural impediment to airflow, allowing easier identification of leaks.

Remove trapped air from the scope’s hollow channels. Trapped air pockets may block the movement of bubbles caused by a leak.

Carefully inspect all material junctions and ports where other parts or devices are attached to the scope.

Stress the bending rubber by angulating the scope in all directions. Look also at the control knobs while turning them to ascertain the “O” rings that support them are not leaking. Some knobs are hollow and trapped air pockets may escape when the knobs are moved.

Gently stress other movable parts such as the forceps raiser or elevator to evaluate their supporting “O” rings.

Slowly massage all of the video switches in a circular pattern while the scope is under water to determine if there are holes. The thick material covering the switches will not always inflate and stretch enough to reveal existing leaks.

Track repairs that include fluid invasion related issues as this typically means there is a need for re-education and competency validation of the team member(s) who have difficulty in discovering leaks.

Observe the scope for no less than 90 seconds. Minimizing this period will handicap your ability to discover leaks as some small leaks may take this long to become noticeable.

Completely remove the scope from the water before turning off the air supply.

Disconnect the leak tester from the air supply and listen for the whoosh of air prior to taking the leak tester off of the scope.

Do not open and then reattach the fluid resistant cap to let air out of the scope as this breaks the seal that has just been validated.

Light guide prongs may loosen as the scope is plugged into or removed from the processor–especially if this movement is from an angle. Tension on the light guide tube during the procedure may also loosen this connection. Should this prong be loose prior to placing the scope in liquids, fluids may be trapped within this pocket. The prong is easily hand tightened; it should not be checked immediately after the procedure as this metal may be hot. However, if the cover remains loose, fluid from the cleaning and reprocessing activities may become trapped inside and subsequently dry on the light guide it should be protecting.

The mechanical air supply unit produces air at a constant force; consequently, leaks are usually identified by a constant flow of bubbles. Should the bubbles flow irregularly, evaluate the site of origin closely. Phantom leaks are typically seen when biopsy/suction channels that have not had the trapped air evacuated or air trapped behind hollow directional knobs have not been effectively evaluated.

At all times, but especially during the leak test, the scope should be isolated from all other items. Items such as some notched valves, biopsy forceps, the metal irrigator that delivers the lidocaine, blunt needle irrigating devices as well as a poorly-fitting basket drain cover can easily scratch or puncture the scope when it is in warm water and its bending rubber is inflated.

An infrequently performed step in minimizing the potential for fluid to invade the scope is to evaluate the video switches. These soft components are easily punctured, may be cut with irrigation port closure devices, or may become dry, brittle, and cracked. Bumping these malleable components against the storage cabinets also causes breakdown in the video switches. By massaging each of these buttons while the scope in under water, holes that would have been missed without this inspection step often open. The #1 switch on many scopes is particularly vulnerable because of its protruding position. Fluid that seeps through undiscovered cracks in the switch plate may evaporate, but it damages the contact points beneath the cover. When this occurs, the ability to control the camera’s function during the procedure may become inconsistent. The camera may either not take pictures, or take unwanted pictures without activation of the switch.

A routine inspection of all fluid resistant caps is advised. This is particularly important if the cap has been dropped and may no longer be round. If the “O” ring is beginning to invert or has inverted, it will not form a seal, and moisture may have collected inside. If there is difficulty in cap placement on the scope, evaluation of the cap’s integrity may be warranted. Once the fluid resistant cap is applied prior to the leak test, it should remain in place until the scope has been completely reprocessed. Should the cap be loosened and then reattached to release pressure after the leak test, the subsequent seal cannot be guaranteed.

Validation of the scope by manual leak testing should include the following considerations:

Lay the scope out in as large a coil as possible.

Securely attach the leak tester.

Pressurize the monometer to the point indicated by the scope’s user manual and within the safe zone.

Shift the directional knobs slowly in all directions.

Move the function levers when present.

Individually massage the video switch buttons.

Monitor the manometer for deflection carefully; a slow leak may take up to 90 seconds to recognize.

Read the instructions that accompany the pressure gauges used within your department. If there is a colored arc indicating pressure, ascertain that all employees know its meanings. Red on one brand can mean too much pressure, but a reading of red on another may indicate effective range.

Pressure should always be applied to the range indicated. Under-pressurizing may allow a leak to go undiscovered; over-pressurizing may lead to damage to “O” ring placement or glue joint or other component security.

A practical habit of always inflating the scope to the same safe level of pressure with each evaluation is prudent. If the manometer is pressurized to the higher parameter within the colored arc or value range and there is a very slow leak, this may not be reflected in the reading because the needle stays within the value range, albeit, the lower end. When the evaluator always starts at the same level, slow deflection is more frequently recognized.

When the manometer’s bulb is squeezed to increase pressure, a vacuum occurs. This basic physics principle should be remembered if the needle deflects downward when the manually pressurized scope is placed in water. When the bulb is depressed to reestablish diagnostic pressure, water can be suctioned into the scope.

In addition to leak testing after each procedure, pressure testing should be performed when trauma occurs to the scope and when the scope returns from repair (regardless of the reason for repair).

Should a leak be identified, a protocol for alternative reprocessing should be established. Substitutes for chemicals and mechanical reprocessing should be made available before a need arises.

Focusing on your area of practice, critically review your practices involving leak testing of endoscopes as it relates to the following list of considerations.

How many holes have been discovered by effective leak testing within the past year?

How many scopes have fluid invasion within the past year?

Is there a specific staff that performs leak tests?

Have others who may fill-in for the designated staff been validated?

Is there a poster or other type of instructions regarding leak testing posted for infrequent performers?

When does leak testing occur?

What is the average length of time for the pressure test?

Are the valves and channel covers removed?

If used, how large is the sink?

Is clear water used for the pressure test?

Is trapped air removed prior to the evaluation?

Are all knobs and levers activated slowly in all directions?

Are the video switch buttons depressed?

Has the scope taken pictures without activation?

Has the scope not taken pictures when the button was depressed?

Is the scope pressurized prior to placing it in water?

Is the scope removed from the water before the scope is depressurized?

Are there other devices in the sink during the test?

Is the drain cover one that can damage the scope?

Is the fluid resistant cap left in place throughout the pressure test and subsequent reprocessing activities?

Are fluid resistant caps in good condition?

Is the scope completely submersed during the test?

If used, is the manometer pressurized within the designated range?

Is there a modified process for cleaning and reprocessing a scope with a known leak?